Initial work on losses_by_period functionality
Initial work on losses_by_period functionality


Former-commit-id: 8728cc6a52181b98f1c055f83b2f791f7bbc0fa8 [formerly 942e30fbc479f66c290f84430cf6357e833c6947]
Former-commit-id: a42a649979b22a7862303ae87c546af9155aa58f
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine